Duggan et al., 2018. Systemative review of pulmonary function and cognition in aging.

Duggan, E.C., Graham, R.B., Piccinin, A.M., Clouston, S., Muniz-Terrera, G., & Hofer, S.M. (2018). A systematic review of pulmonary function and cognition in aging. The Journal of Gerontology: Series B, gby128. DOI: https://doi.org/10.1093/geronb/gby128

Year: 
2018
Status: 
complete
Abstract: 

Background: Substantial research is dedicated to understanding the aging-related dynamics among individual differences in level, change, and variation across physical and cognitive abilities. Evaluating replicability and synthesizing findings has been limited by differences in measurements, samples, study design and statistical analyses which confound between-person differences with within-person changes. Here, we systematically reviewed longitudinal results on the aging-related dynamics linking pulmonary function and cognitive performance.

Methods: PRISMA guidelines were used to systematically review longitudinal studies of pulmonary function and cognition.

Results: Only four studies thoroughly investigating cognitive and pulmonary longitudinal associations (three or more measurement occasions) were identified. Expanded review criteria identified three studies reporting two measurement occasions, and seven studies reporting one measurement of pulmonary function or cognition and two or more measurements of the other. We identified numerous methodological quality and risk for bias issues across studies.

Conclusions: Despite documented correlational associations between pulmonary function and cognition, these results show there is very limited research thoroughly investigating their longitudinal associations. This highlights the need for longitudinal data, rigorous methodological design including key covariates, and clear communication of methods and analyses to facilitate replication across an array of samples. We recommend systematic study of outcome measures and covariates, inclusion of multiple measures (e.g., PEF, FEV1, and FVC), as well as application of the same analytic approach across multiple datasets.

Zammit et al., 2018. Associations between aging-related changes in grip strength and cognitive function in older adults: A systematic review.

Zammit, A.R., Robitaille., A., Piccinin, A.M., Muniz-Terrera, G. & Hofer, S.M. (2018). Associations between aging-related changes in grip strength and cognitive function in older adults: A systematic review. Journal of Gerontology: Medical Sciences: Series A. DOI: 10.1093/gerona/gly046

Year: 
2018
Status: 
complete
Abstract: 

Objectives. Grip strength and cognitive function reflect upper body muscle strength and mental capacities. Cross-sectional research has suggested that in old age these two processes are moderately to highly associated, and that an underlying common cause drives this association. Our aim was to synthesize and evaluate longitudinal research addressing whether changes in grip strength are associated with changes in cognitive function in healthy older adults.

Methods. We systematically reviewed English-language research investigating the longitudinal association between repeated measures of grip strength and of cognitive function in community-dwelling older adults to evaluate the extent to which the two indices decline concurrently. We used four search engines: Embase, PsychINFO, PubMed, and Web of Science.

Results. Of 459 unique citations, 6 met our full criteria: 4 studies reported a longitudinal association between rates of change in grip strength and cognitive function in older adults, 2 of which reported the magnitudes of these associations as ranging from low to moderate; 2 studies reported significant cross-sectional but not longitudinal associations among rates of change. All studies concluded that cognitive function and grip strength declined, on average, with increasing age, although with little to no evidence for longitudinal associations among rates of change.

Conclusions. Future research is urged to expand the study of physical and cognitive associations in old age using a within-person and multi-study integrative approach to evaluate the reliability of longitudinal results with greater emphasis on the magnitude of this association

Karr et al., 2018. When does cognitive decline begin?

Karr, J. E., Graham, R. B., Hofer, S. M., & Muniz-Terrera, G. (2018). When does cognitive decline begin? A systematic review of change point studies on accelerated decline in cognitive and neurological outcomes preceding mild cognitive impairment, dementia, and death. Psychology and Aging, 33(2), 195-218.

Year: 
2018
Status: 
complete
Abstract: 

Older adults who ultimately develop dementia experience accelerated cognitive decline long before diagnosis. A similar acceleration in cognitive decline occurs in the years before death as well. To evaluate preclinical and terminal cognitive decline, past researchers have incorporated change points in their analyses of longitudinal data, identifying point estimates of how many years prior to diagnosis or death that decline begins to accelerate. The current systematic review aimed to summarize the published literature on preclinical and terminal change points in relation to mild cognitive impairment (MCI), dementia, and death, identifying the order in which cognitive and neurological outcomes decline and factors that modify the onset and rate of decline. A systematic search protocol yielded 35 studies, describing 16 longitudinal cohorts, modeling change points for cognitive and neurological outcomes preceding MCI, dementia, or death. Change points for cognitive abilities ranged from 3–7 years prior to MCI diagnosis, 1–11 years prior to dementia diagnosis, and 3–15 years before death. No sequence of decline was observed preceding MCI or death, but the following sequence was tentatively accepted for Alzheimer’s disease: verbal memory, visuospatial ability, executive functions and fluency, and last, verbal IQ. Some of the modifiers of the onset and rate of decline examined by previous researchers included gender, education, genetics, neuropathology, and personality. Change point analyses evidence accelerated decline preceding MCI, dementia, and death, but moderators of the onset and rate of decline remain ambiguous due to between-study modeling differences, and coordinated analyses may improve comparability across future studies. (PsycINFO Database Record (c) 2018 APA, all rights reserved)

 

Griffith et al., 2015.Statistical approaches to harmonize data on cognitive measures in systematic reviews are rarely reported

Griffith, L. E., Van Den Heuvel, E., Fortier, I., Sohel, N., Hofer, S. M., Payette, H., Wolfson, C., Belleville, S., Kenny, M., Doiron, D., & Raina, P. (2015). Statistical approaches to harmonize data on cognitive measures in systematic reviews are rarely reported. Journal of clinical epidemiology, 68(2), 154-162.

Year: 
2015
Status: 
complete
Abstract: 

Objectives. To identify statistical methods for harmonization, the procedures aimed at achieving the comparability of previously collected data, which could be used in the context of summary data and individual participant data meta-analysis of cognitive measures.

Study Design and Setting. Environmental scan methods were used to conduct two reviews to identify (1) studies that quantitatively combined data on cognition and (2) general literature on statistical methods for data harmonization. Search results were rapidly screened to identify articles of relevance.

Results. All 33 meta-analyses combining cognition measures either restricted their analyses to a subset of studies using a common measure or combined standardized effect sizes across studies; none reported their harmonization steps before producing summary effects. In the second scan, three general classes of statistical harmonization models were identified (1) standardization methods, (2) latent variable models, and (3) multiple imputation models; few publications compared methods.

Conclusion. Although it is an implicit part of conducting a meta-analysis or pooled analysis, the methods used to assess inferential equivalence of complex constructs are rarely reported or discussed. Progress in this area will be supported by guidelines for the conduct and reporting of the data harmonization and integration and by evaluating and developing statistical approaches to harmonization.

Munoz et al., 2015. Global perceived stress predicts cognitive change among older adults.

Munoz, E., Sliwinski, M. J., Scott, S. B., & Hofer, S. (2015). Global perceived stress predicts cognitive change among older adults. Psychology and aging, 30(3), 487.

Year: 
2015
Status: 
complete
Abstract: 

Research on stress and cognitive aging has primarily focused on examining the effects of biological and psychosocial indicators of stress, with little attention provided to examining the association between perceived stress and cognitive aging. We examined the longitudinal association between global perceived stress (GPS) and cognitive change among 116 older adults (Mage = 80, SD = 6.40, range = 67–96) in a repeated measurement burst design. Bursts of 6 daily cognitive assessments were repeated every 6 months over a 2-year period, with self-reported GPS assessed at the start of every burst. Using a double-exponential learning model, 2 parameters were estimated: (a) asymptotic level (peak performance), and (b) asymptotic change (the rate at which peak performance changed across bursts). We hypothesized that greater GPS would predict slowed performance in tasks of attention, working memory, and speed of processing and that increases in GPS across time would predict cognitive slowing. Results from latent growth curve analyses were consistent with our first hypothesis and indicated that level of GPS predicted cognitive slowing across time. Changes in GPS did not predict cognitive slowing. This study extends previous findings by demonstrating a prospective association between level of GPS and cognitive slowing across a 2-year period, highlighting the role of psychological stress as a risk factor for poor cognitive function. (PsycINFO Database Record (c) 2018 APA, all rights reserved)

Weuve et al., 2015. Guidelines for reporting methodological challenges and evaluating potential bias in dementia research

Weuve, J., Proust-Lima, C., Power, M. C., Gross, A. L., Hofer, S. M., Thiébaut, R., Chêne, G., Glymour, M.M., Dufouil, C, & MELODEM Initiative. (2015). Guidelines for reporting methodological challenges and evaluating potential bias in dementia research. Alzheimer's & Dementia, 11(9), 1098-1109.

Year: 
2015
Status: 
complete
Abstract: 

Clinical and population research on dementia and related neurologic conditions, including Alzheimer's disease, faces several unique methodological challenges. Progress to identify preventive and therapeutic strategies rests on valid and rigorous analytic approaches, but the research literature reflects little consensus on “best practices.” We present findings from a large scientific working group on research methods for clinical and population studies of dementia, which identified five categories of methodological challenges as follows: (1) attrition/sample selection, including selective survival; (2) measurement, including uncertainty in diagnostic criteria, measurement error in neuropsychological assessments, and practice or retest effects; (3) specification of longitudinal models when participants are followed for months, years, or even decades; (4) time-varying measurements; and (5) high-dimensional data. We explain why each challenge is important in dementia research and how it could compromise the translation of research findings into effective prevention or care strategies. We advance a checklist of potential sources of bias that should be routinely addressed when reporting dementia research.

    Rast et al., 2014. The identification of regions of significance in the effect of multimorbidity on depressive symptoms using longitudinal data: an application of the Johnson-Neyman technique.

    Rast, P., Rush, J., Piccinin, A., & Hofer, S. M. (2014). The identification of regions of significance in the effect of multimorbidity on depressive symptoms using longitudinal data: An application of the Johnson-Neyman technique. Gerontology60(3), 274-281.

    Year: 
    2014
    Status: 
    complete
    Abstract: 

    Background: The investigation of multimorbidity and aging is complex and highly intertwined with aging-related changes in physical and cognitive capabilities, and mental health and is known to affect psychological distress and quality of life. Under these circumstances it is important to understand how the effects of chronic conditions evolve over time relative to aging-related and end-of-life changes. The identification of periods in time where multimorbidity impacts particular outcomes such as depressive symptoms, versus periods of time where this is not the case, reduces the complexity of the phenomenon. 

    Objective: We present the Johnson-Neyman (JN) technique in the context of a curvilinear longitudinal model with higher-order terms to probe moderatorst and to identify regions of statistical significance. In essence, the JN technique allows one to identify conditions under which moderators impact an outcome from conditions where these effects are not significant. 

    Methods: To illustrate the use of the JN technique in a longitudinal sample, we used data from the Health and Retirement Study. Analyses were based on time-to-death models including participants who died within the study duration of 12 years. 

    Results: Multimorbidity differentially affects rates of change in depression. For some periods in time the effects are statistically significant while in other periods the same effects are not statistically different from zero. 

    Conclusion: The JN technique is useful to continuously probe moderating effects and to identify particular interactions with the model for time when certain effects are or are not statistically significant. In the context of multimorbidity this method is particularly useful for interpreting the complex interactions with differential change over time.

    Muniz-Terrera et al., 2012. Investigating terminal decline: results from a UK population-based study of aging.

    Muniz-Terrera, G., van den Hout, A., Piccinin, A. M., Matthews, F. E., & Hofer, S. M. (2013). Investigating terminal decline: Results from a UK population-based study of aging. Psychology and aging, 28(2), 377.

    Year: 
    2012
    Status: 
    complete
    Abstract: 

    The terminal decline hypothesis states that in the proximity of death, an individual’s decline in cognitive abilities accelerates. We aimed at estimating the onset of faster rate of decline in global cognition using Mini Mental State Examination (MMSE) scores from participants of the Cambridge City over 75 Cohort Study (CC75C), a U.K. population-based longitudinal study of aging where almost all participants have died. The random change point model fitted to MMSE scores structured as a function of distance to death allowed us to identify a potentially different onset of change in rate of decline before death for each individual in the sample. Differences in rate of change before and after the onset of change in rate of decline by sociodemographic variables were investigated. On average, the onset of a faster rate of change occurred about 7.7 years before death and varied across individuals. Our results show that most individuals experience a period of slight decline followed by a much sharper decline. Education, age at death, and cognitive impairment at study entry were identified as modifiers of rate of change before and after change in rate of decline. Gender differences were found in rate of decline in the final stages of life. Our study suggests that terminal decline is a heterogeneous process, with its onset varying between individuals. (PsycINFO Database Record (c) 2016 APA, all rights reserved)

    Clouston et al., 2015. Educational Inequalities in Health Behaviors at Midlife: Is There a Role for Early-life Cognition?

    Clouston, S. A., Richards, M., Cadar, D., & Hofer, S. M. (2015). Educational inequalities in health behaviors at midlife: Is there a role for early-life cognition? Journal of health and social behavior, 56(3), 323-340.

    Year: 
    2015
    Status: 
    complete
    Abstract: 

    Education is a fundamental cause of social inequalities in health because it influences the distribution of resources, including money, knowledge, power, prestige, and beneficial social connections, that can be used in situ to influence health. Recent studies have highlighted early-life cognition as commonly indicating the propensity for educational attainment and determining health and age of mortality. Health behaviors provide a plausible mechanism linking both education and cognition to later-life health and mortality. We examine the role of education and cognition in predicting smoking, heavy drinking, and physical inactivity at midlife using data from the Wisconsin Longitudinal Study (N = 10,317), National Survey of Health and Development (N = 5,362), and National Childhood Development Study (N = 16,782). Adolescent cognition was associated with education but was inconsistently associated with health behaviors. Education, however, was robustly associated with improved health behaviors after adjusting for cognition. Analyses highlight structural inequalities over individual capabilities when studying health behaviors.

    Clouston et al., 2015. Educational inequalities in aging-related declines in fluid cognition and the onset of cognitive pathology

    Clouston, S. A., Glymour, M. M., & Terrera, G. M. (2015). Educational inequalities in aging-related declines in fluid cognition and the onset of cognitive pathology. Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring, 1(3), 303-310.
    Year: 
    2015
    Status: 
    complete
    Abstract: 

    Background: Education has been robustly associated with cognitive reserve and dementia, but not with the rate of cognitive aging, resulting in some confusion about the mechanisms of cognitive aging. This study uses longitudinal data to differentiate between trajectories indicative of healthy versus pathologic cognitive aging.

    Methods: Participants included 9401 Health and Retirement Study respondents aged ≥55 years who completed cognitive testing regularly over 17.3 years until most recently in 2012. Individual-specific random change-point modeling was used to identify age of incident pathologic decline; acceleration is interpreted as indicating likely onset of pathologic decline when it is significant and negative.

    Results: These methods detect incident dementia diagnoses with specificity/sensitivity of 89.3%/44.3%, 5.6 years before diagnosis. Each year of education was associated with 0.09 (95% confidence interval [CI], 0.087–0.096; P < .001) standard deviation higher baseline cognition and delayed onset of cognitive pathology (hazard ratio, 0.98; 95% CI, 0.96–0.99; P = .006).

    Conclusions: Longitudinal random change-point modeling was able to reliably identify incident dementia. Accounting for incident cognitive pathology, we find that education predicts cognitive capability and delayed onset pathologic declines.

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